This disclosure relates to testing operations of light emitting diodes (LEDs) mounted on a substrate, more specifically to testing operations of microLEDs using probe pads embedded in the substrate.
Light emitting devices, such as micro LEDs (μLEDs) are used in electronic display panels to emit light for image production. Such electronic display panels may involve picking up and placing LED dies on a substrate. Each electronic display panel may include a large number of LEDs (e.g., 1280 LEDs for each color). If an LED die contains 20 LEDs of the same color, 64 dies are picked and placed on the substrate of the electronic display panel for each color. After all of the LED dies are placed onto the substrate, each of the LEDs are probed individually to detect whether the LEDs on the electronic display panel turn on.
However, individually probing a large number of the LEDs on the substrate is costly and time consuming. Further, even if the LEDs placed early during a fabrication process are defective or not correctly connected, probing of the LEDs is typically performed after all the LEDs are mounted on the substrate. This may lead to wasted LEDs and assembly time because the substrate with defective LEDs is not identified until all the LEDs are mounted onto the substrate.